Ringer assemblies with volume controls of various types are generally known in the telephone arts. In more recent Bell System phones, the control is effected by an eccentric rotary adjustment of one gong which is truck by the clapper. For example, see U.S. Pat. No. 2,590,500 to Bredehoft et al issued 3/25/52 for a showing of the ringer assembly in use in the Bell 500 series telephones.
In that patent, the gongs are mounted on mounting axes essentially parallel to position of the clapper arm in its normal position. A rotatable control wheel is mounted on the stationary assembly frame. The wheel mounting allows rotation of the wheel relative to the assembly. The wheel has a sector of its periphery extending through a slot in the undersurface of the telephone base to enable manual rotation of the wheel through an arc of predetermined extent.
One gong is mounted on the sheel with its mounting eccentric to the wheel mounting. On rotation of the wheel, the gong periphery opposite the clapper describes a path varying the distance from clapper to gong. By rotating the wheel, the distance of the gong periphery from the clapper is varied to vary the volume of the ringing emanating from the gong.
To hold the wheel and gong in a position once set and yet enabling the position to be overcome by the manual motion of the thumbwheel a flat spring is mounted to rotate with the wheel. The flat spring has a boss which mates with suitable indentations in the assembly frame to hold the wheel once set. The mating of the boss in an indentation may be overcome by manual rotative force applied to the wheel.
Further, the flat spring has a second arm which offset outwardly of the wheel periphery to engage travel limit stops extending radially on the frame edge. A finger raised from the plane of the wheel engages one side of the wheel travel limit arm to hold the arm in place and make the rotation and limit stop a more rigid structure.